1. Field of the Invention
The present invention relates to a method of cleaning a cover glass and, more particularly, to a method of cleaning a cover glass having a spacer during the manufacture of a chip size package (CSP) type solid image pickup device.
2. Description of the Related Art
A solid image pickup device formed from a CCD or a CMOS, which is used in digital cameras and cellular phones, is required to be more and more miniaturized. For this reason, at present there is a shift from conventional large-size packages, such as a type in which the whole solid image pickup element chip is hermetically sealed in a package of ceramics and the like, to a chip size package (CSP) type having almost the same size as the size of a solid image pickup device.
Against this background, there have been proposed methods by which a spacer is formed on a transparent glass plate corresponding to a position surrounding the photo-detecting portion of each of the solid image pickup elements which are formed in a large number on a wafer (a semiconductor substrate), this transparent glass plate is bonded to the wafer in a spacer portion to form a void part between the transparent glass plate and the wafer, and after that, the transparent glass plate and the wafer are diced along scribe lines, whereby the transparent glass plate and the wafer are separated into individual solid image pickup devices (refer to Japanese Patent Application Laid-Open No. 7-202152 and Japanese Patent Application Laid-Open No. 2002-231921, for example).
It is general practice to adopt dry etching as a method of forming a spacer on such a transparent glass plate as described above. FIGS. 7A to 7C are sectional views of a step of forming this spacer. In FIG. 7A, a spacer substrate which becomes a spacer 13 is bonded to a surface of a cover glass 12, which corresponds to a transparent glass plate, via an adhesive 13A. Subsequently, a pattern of a photoresist R as an etching mask is formed on a surface of this spacer substrate.
For example, a silicon wafer can be used as the spacer substrate which becomes the spacer 13. The pattern of the photoresist R is formed by going through the steps of exposure using a resist coat and a photomask, development, post bake and the like.
Subsequently, in FIG. 7B, the anisotropic etching of the spacer substrate (the silicon wafer) which becomes the spacer 13 is performed by dry etching and a pattern of the spacer is formed. On this occasion, the adhesive 13A, which has etching resistance, is not removed.
Subsequently, in FIG. 7C, ashing is performed and the pattern of the photoresist R and the exposed adhesive 13A are removed. In this manner, the pattern of the space 13 is formed on the surface of the cover glass 12.